Electronic mail systems are known as typical systems for transmitting and receiving messages between user terminals. In an electronic mail system, a Simple Mail Transfer Protocol (SMTP) server transfers electronic mail transmitted from a user to a Post Office Protocol (POP) server. The POP server stores transferred electronic mail. Users attempting to receive electronic mail retrieve the electronic mail by accessing the POP server. A chat system is known as a system to transmit and receive messages between user terminals in real time. In a chat system, messages entered by participants are displayed in real time when a user terminal connects to a chat server. User terminals can also transmit messages to participants.    [patent document No. 1] U.S. Pat. No. 6,563,999
In an electronic mail system, messages are retrieved when the user accesses a POP server. As such, an electronic mail system is inferior to a chat system in terms of responsiveness in information transmission. While a chat system is an excellent tool in terms of responsiveness in information transmission, users cannot be provided with messages without on-line connection to a chat server via, for example, the Internet. This calls for development of a system capable of receiving messages matching the situation in a responsive manner without on-line connection.